1. Field of the Invention
The present invention relates generally to electronic device testing, and more particularly, to testing of integrated circuit (IC) devices exhibiting non-deterministic behavior.
2. Description of the Related Art
Next generation microprocessors will use a large number of high-speed serial links to communicate with external memory and I/O devices. High-speed serial links in general exhibit a non-deterministic behavior during data transmission. The conventional automated test equipment (ATE) available in the marketplace does not have a test methodology to deal with this non-determinism, and is not able to perform validation and production testing of these devices.
As illustrated in the table below, the conventional ATE uses stored stimulus patterns (D1, D2, D3, etc.) to drive the device under test at set time intervals (t1, t2, t3, etc.). The conventional ATE then compares the response signals from the device under test with stored response patterns (E1, E2, E3, etc.) at each of the set time intervals (t1, t2, t3, etc.). A fail trigger is issued if there is a mismatch between the actual response signal and the stored response pattern.
TimeDriveExpectActualt1D1E1E1t2D2E2E2t3D3E3E3t4D4E4E4t5D5E5E5t6D6E6E6t7D7E7E7t8D8E8E8t9D9E9E9
This test methodology works as long as the device under test exhibits deterministic behavior, i.e., a one-to-one correspondence between the drive signal and the response signal is expected. Some ICs, however, exhibit non-deterministic behavior (e.g., in response to certain inputs, the device under test idles prior to exhibiting a response), and the test methodology used in conjunction with the conventional ATE is not able to perform validation and production testing of these devices. The table below shows a sample response of an IC that exhibits non-deterministic behavior. If the conventional test methodology is used in testing this IC, all comparisons after t1 will result in a fail trigger.
TimeDriveExpectActualt1D1E1E1t2D2E2idlet3D3E3E2t4D4E4idlet5D5E5idlet6D6E6E3t7D7E7E4t8D8E8idlet9D9E9E5